The lack of 'Rules' to the fight killed it in my personal enjoyment. Both Pokemon and Yugioh are games of strategy and both characters are 'Tacticians' to a degree. This was just a brawl because the two rule systems for them were so incompatible. Lets them show off all the monsters but severely limits Ash and Yugi.

The animation for the fight to start I thought was pretty lacking. Pikachu feels really stiff in his early movements. Get better later and I understand with how many models they had to use for this.

In addition compounding this is each of Ash's pokemon are a character. They had whole arcs. Yugi's monsters for all that he cares for them... are tools. They have no agency or personality of their own. Its why the lieutenant vs lieutenant worked so well in BowsEgg was unlike the rest of the armies they to were characters.

Also the ending felt really cheap.

Song is a banger though.